Testicular cancer develops in the testicles, the male reproductive glands. The testicles are located in the membranous pouch below the penis (scrotum) and are suspended from the body by the spermatic cord. They produce male reproductive cells (sperm) and testosterone. Testicular cancer is treated successfully in more than 95% of cases.

Incidence and Prevalence

Around half of all cases occur in men under 35 years and over 90% occur in men under 55 years. Testicular cancer rarely occurs before puberty but it is the most common cancer in men aged 15-44 years. Incidence rates peak at around 17 to 18 per 100,000 in the 25-34 age groups. In 2006 there were around 2,065 new cases of testicular cancer diagnosed in the UK. It is approximately 5 times more common in Caucasians than African Americans. Germany, Scandinavia, and New Zealand have the highest incidence of testicular cancer and Asia and Africa have the lowest.

Types of Testicular Cancer

Most testicular cancer originates in undeveloped cells (germ cells) that produce sperm. These tumours, called germ cell tumours (GCTs), are most common in men between the ages of 20 and 40 and are curable in more than 95% of cases. There are two main types: seminomas and nonseminomas. A third type, called stromal tumours, develops in the supporting tissues of the testicle.

Typical seminomas account for 90% of this type. They often cause unilateral (i.e., on one side) testicle enlargement or more often a painless lump in the testicle. Spermatocytic seminomas grow slowly, usually do not spread to other parts of the body (metastasise), and are most common around age 65.

Nonseminomas account for 60% of GCTs and develop in younger men (usually between 15 and 35). Most nonseminomas contain cells from at least two subtypes, including the following:

Choriocarcinoma (rare; aggressive; likely to metastasise)

Embryonal carcinoma (accounts for 20% of cases; likely to metastasise)

Teratoma (usually benign in children; rarely metastasise)

Yolk sac carcinoma (most common in young boys; rare in men)

Testicular cancer may also develop in the supportive, hormone-producing tissue of the testicles (stroma). This type accounts for 4% of testicular cancer in men and 20% in boys. Types of stromal tumours include Leydig cell tumours and Sertoli cell tumours.

Seventy-five percent of Leydig cell tumours develop in men and 25% develop in boys. Most tumours of this type are benign and are treated successfully with surgery. If the tumour metastasises, it often does not respond well to radiation or chemotherapy and the prognosis is poor.

Sertoli cell tumours develop in Sertoli cells that nourish the sperm-producing germ cells. These tumours are usually benign; metastatic tumours of this type are rare, yet resistant to treatment.

Secondary tumours in the testicles usually migrate from the lymph or lymph nodes. Testicular lymphoma is more common than primary testicular cancer in men over 50. Other cancers (e.g., prostate, lung, skin) may also spread to the testicles.

Risk Factors

The major risk factors for testicular cancer are cryptorchidism (i.e., a condition in which the testes do not descend into the scrotum; also called undescended testicle) and Klinefelter's syndrome (i.e., a congenital disorder caused by an extra X chromosome that results in failure of the testicles and usually is diagnosed after puberty). Other risk factors include a family or personal history of testicular cancer and genetic abnormality of chromosome 12.

Causes

The cause of testicular cancer is unknown. One theory suggests that testicular germ cell tumours form when germ cells develop into sperm cells with 46 chromosomes. Normally, germ cells with 46 chromosomes develop into sperm cells with 23 chromosomes (during a process called meiosis).

Signs and Symptoms

Testicular cancer does not always produce symptoms. A mass or lump in the testicle is usually the first sign of the disease. The mass may or may not be painful. Other symptoms include testicular swelling, hardness, and a feeling of heaviness or aching in the scrotum or lower abdomen.

Testicular cancer that has spread to other organs (metastasised) may cause lower back pain, shortness of breath, chest pain, and cough.

Diagnosis

Diagnosis of testicular cancer involves a patient history, physical examination, and diagnostic tests. A patient history is taken to evaluate risk factors. During physical examination the physician fells the testicles and the abdomen to detect a lump, swelling, or enlarged lymph nodes. Diagnostic tests include ultrasound, CT scan, and blood tests.

Testicular Self-Examination

Physicians routinely examine the testicles during a physical. But monthly testicular self-examinations (TSE) are recommended after puberty, especially for men at increased risk for testicular cancer. Finding testicular tumours early increases the chance for curing the disease.

The best time to perform the exam is during or after a warm bath or shower, when the skin of the scrotum is relaxed. Examine each testicle gently with both hands. The index and middle fingers should be placed underneath the testicle, and the thumbs placed on the top. Roll the testicle gently between the thumbs and fingers.

One testicle may feel larger than the other. This is normal. You will also feel a cord-like structure on the top and back of the testicle that stores and transports the sperm. This is the epididymis and should not be confused with an abnormal lump.

If you find an abnormal lump on the front or the side of the testicle, make an appointment to see your doctor immediately. If the lump is caused by an infection, the doctor can prescribe treatment. If the lump is not an infection, your general practitioners will refer you to a urologist to determine if it is a tumour.